The present invention generally relates to a rotary type electric razor.
Generally, there are some rotary type electric razors which include an internal cutting edge driving unit with a rotary internal cutting edge, a motor and a drive transmitting means for transmitting the motor output to the rotary cutting edge being integrally engaged with an internal driving chassis. The internal cutting edge is adapted to be brought into closer contact with the internal surface of the external cutting edge with the internal cutting edge driving unit being normally urged to be pushed up with a leaf spring within the main body case (literature cited not known).
Further, there are other reciprocating type electric razors as described in, for example, Japanese Laid-Open Patent Application No. 61-62381, wherein the number of revolutions of the driving motor is normally detected in order to retain the speed of the motor despite the light weight variation of the load to make it possible to effect the shaving operation under optimum conditions.
Further, there are some detecting means for detecting the number of revolutions of the motor of the electric razor as shown in, for example, Japanese Laid-Open Utility Model Application No. 62-10880, wherein a non-contact type reflection photosensor is used to detect reflection marks on the output shaft of the motor so as to detect the number of revolutions of the motor (i.e. motor speed) in accordance with the pulse-shaped output from the photosensor.
A problem occurs, however, when a non-contact type of revolution number sensor for detecting revolution of the motor output shaft is engaged in a rotary type electric razor. That is, the internal edge driving unit is required to be moved straight in the vertical direction so as to avoid detection errors. When the motor output shaft is tilted during vertical motion of the internal cutting edge driving unit, the position shift with respect to the opposing photosensor results in detection errors.
In the rotary type electric razor, the internal cutting edge driving unit is simply supported by only a leaf spring within the main body case when the internal cutting edge driving unit is engaged in a condition where it is normally urged to be pushed up into the main body case, such that it is unstable with respect to positional control in the longitudinal and right and left directions. When the external cutting edge is moved between a position pressed against the skin and a position away from the skin, the internal cutting edge driving unit which includes the motor is caused to move vertically and becomes inclined due to variations in the pressing position and the pressing force. The rotary member to be detected by the photosensor can slip out of place so that errors in detecting the number of revolutions of the motor by the photosensor are likely.